Thanx. You don't need any tutorials for this, they're fairly easy to make. On almost every tool, there is a transparancy slider.

Just create a new image, 1 px x the height you want (I used 24 px).

Set a gradient you like on the gradient tab, select the gradient tool and play around with the settings on the gradient tool to get results. The rectangle select and the grandient tool is the key to theese ;)